Earthquakes Cause Significant Damage to Lives and Property. However, recent research suggests that earthquakes may actually help trees in the valley grow as well as those on the hillsides by providing more water to their roots.
After an earthquake, hydrologist Christian Mohr from the University of Potsdam and his colleagues drilled 20 wood samples from 6 Monterey pine trees along the slopes from high to low in the valley and mountainside.
Each sample was the size of a pencil. They analyzed the wood cores under a microscope, tracking how the size and shape of cells in the tree’s growth rings changed when more water was available.
They then measured the ratios of carbon-12 and carbon-13 isotopes and how they varied among different cells. Trees absorb more carbon-12 than carbon-13 during photosynthesis, so the changes in carbon isotope ratios among cells of different ages indicate periods of heightened photosynthetic activity in the past. These periods also correspond to times when trees received more water, as water is essential for the photosynthesis process.
Trees absorb nutrients from roots after each earthquake. (Illustrative image)
From the cell shapes and carbon isotope ratios, Mohr’s team discovered that trees at the bottom of the valley experienced a significant growth spurt lasting weeks to months after the earthquake in Maule—a growth increase comparable to that caused by heavy rainfall. As initially predicted, trees on the hillsides, at higher elevations, grew more slowly after the earthquake, the team reported in the Journal of Geophysical Research Biogeosciences.
Panyushkina noted that this technique could be used to accurately determine when earthquakes, heavy rains, and other events triggered short-term growth impacts.
Since the growth rings of trees reflect average growth over each year, researchers could only use them to identify earthquakes, volcanic eruptions, and tsunamis within a range of years. By combining additional cellular-level measurements with carbon isotope data, Mohr and colleagues were able to pinpoint the Maule earthquake with monthly accuracy.
The next step is to replicate the study at other locations to see if the technique applies to different tree species and climates. In Chile, Monterey pines are often planted in arid areas, which limits tree growth, making it easier to observe growth surges due to additional water.
Mohr also believes that the new technique will be most accurate in relatively arid regions, where trees show clearer growth when water is available. He plans to repeat the study with tree cores from Napa Valley in California.
According to Panyushkina, this method could also assist historians in looking back at the past: identifying short-term disturbances like earthquakes that occurred thousands of years ago. Accurately determining ancient earthquakes and other events that impacted groundwater will be “important for geological, hydrological, and societal purposes,” Panyushkina said, “This research has provided a new technique and tool.”
